Well, there was precedent for such a replacing of starring characters. The first time it happened was in the 1988-1989 when they replaced the actor who played Commander Riker in the first season with another guy in the second who had a beard.
I like the bearded Riker better. That beard defeated Locutus of Bored..I mean Borg.
Defeated? Locutus, played by a fine Roman actor (you can tell by the accent), became the new captain after that Frenchman left.